Looking for ideas on P0300 code

[wulfden]

Here is my situation: I have a 2000 LS-2 with over 100,000 miles on it. On a recent trip I got caught in a bad storm and had to cross an intersection with standing water. The water was deep (about a foot), I made it to my destination just fine, and it ran normally the rest of the day. The next day the "service engine soon" started blinking and I noticed the car feeling sluggish. Within 5 minutes the light was on steady and the car was losing power. I stopped for about an hour, when I started it, it ran rough. As I was leaving the parking lot I heard something let loose in the engine compartment (like a belt), after that it would barely run enough to limp into a parking stall. The serpentine belt was shredded up a bit and it ran like it was badly out of time. I got he car home and I replaced the timing belt and serpentine belt. That changed nothing, it ran exactly the same. I plugged in the scanner and I got the code P0300-(Random/Multiple Cylinder Misfire Detected), that was the only code that came up. I am unsure of where to go from here and would greatly appreciate any help.

[fdryer]

Both timing and serpentine belts were replaced? Losing the plain serp belt is one thing as all it does, if soaked, would be to allow belt slippage and some loss of electrical power from the alternator not maintaining the power to the car and forcing the battery to supply main power. You'd also feel the power steering loss by the stiff steering wheel. Minor things but the timing belt is the important one and a shredded one is not good. Loss of timing can either result in poor engine running to extreme damage from pistons meeting valves for skipped teeth/mistiming.

Which belt was severely damaged and if you replaced the timing belt, are you sure timing is correct? One member replaced his timing belt and chased his tail around trying to figure out poor engine running when it was discovered that the timing was off a single tooth. Putting in your own bugs is one of the biggest mistakes we all do from time to time and misleads everyone.

If you are sure the timing is perfect, pull the battery negative cable for 5-minutes to reset the error code and start the engine to see if the error code comes back. Check that the battery is at operational voltage, at least 12.5v, 13.5v-14.5v engine running.

[wulfden]

Thanks for the reply,
Yes, I replaced both belts, the serpentine belt is the one that was in rough shape. The timing belt looked pretty good and was still in time. I replaced the timing belt and am sure that it is in time also. The battery is also fully charged.
After clearing the codes I rescanned and the same code came up P0300. The engine contiues to barely run and backfires at low speed, at higher rpms (3000rpm) it smooths out and sounds better.
I am wondering if the serpentine belt starting to come apart might have hit something???
The engine runs the same after replacing the timing belt as it did with the original timing belt. It seems as though it could be one of many different things and I don't know what to do next. I may have to tow it to the shop to see if they can find something.
Any more ideas would be greatly appreciated!!!

[fdryer]

The serp belt coming apart just lets the battery run down a the alternator no longer supplies all the electrical needs of the car, the water pump not running will allow the engine to overheat, and you lose power steering.

Have you replaced the spark plugs yet? 100,000 mile replacement interval. Try the easy things first.

[wulfden]

Yes- sorry I forgot to mention that I did replace the plugs with the timing belt. The old plugs looked pretty good, no signs of anything going on in there.

[alfelten]

Did you ever workout what was the problem?